Rockfill materials are widely employed in dam construction, with their deformation and strength critically dependent on particle-size distribution. Various gradation scaling techniques are adopted to accommodate the laboratory apparatus size by converting the grading of realistic rockfill materials into a reasonable range. However, these gradation transformations can introduce significant disparity in the mechanical behavior compared to the original prototype. In this study, the discrete element method (DEM) is used to compare the mechanical properties of rockfill material using different gradation scaling techniques such as equivalent substitution, scalping, and similar grading methods. One-dimensional compression and drained triaxial tests are conducted while the macroscopic and microscopic properties are analyzed. The findings reveal that gradation scaling techniques significantly affect the compressibility and strength of rockfill materials, as indicated by the variations in the microscopic parameters.